Axial piston engine comprising a return device

ABSTRACT

The invention relates to an axial piston engine ( 1 ) comprising a housing ( 2 ) wherein a cylinder drum ( 17 ) is arranged. Several axially extending piston bores ( 21 ) are embodied in the cylinder drum and arranged in such a way that they are distributed around the longitudinal center axis ( 7   a ) of the cylinder drum ( 17 ). Pistons ( 23 ) are moveably guided in said bores and are supported by sliding shoes ( 29 ) on a pivoting mounted on a transversely extending pivoting axis ( 27 ). A stop ( 44   b ) or a stop ( 44   a,    44   b ) on both sides of the pivoting axis ( 27 ) is/are provided in order to limit the pivoting movements of the pivoting plate ( 26 ). In order to stabilise the axial piston engine and provide it with a simple design, the stop ( 44   b ) or both stops ( 44   a,    44   b ) are arranged on a sleeve-like supporting element ( 45 ) which is supported by the inner covering surface ( 3   c ) of the inside of the housing ( 4 ).

[0001] The invention relates to an axial piston engine according to thepreamble of claim 1, 5 or 6.

[0002] An axial piston engine having a swivel plate capable ofswivelling about a swivelling axis is an axial piston engine with avariable throughput rate. Said rate may be adjusted by means of aso-called adjusting apparatus, by means of which the swivel plate may beswivelled and locked in the respective desired swivel position. Saidadjusting apparatus may be an apparatus, by means of which the swivelplate is adjustable only between its swivel end positions, i.e. betweenthe minimum and the maximum rate setting, or an adjusting apparatus, bymeans of which the swivel plate is adjustable and lockable also inintermediate positions between the swivel end positions, wherein thedelivery rate is e.g. infinitely adjustable.

[0003] Particularly in an axial piston engine of the type, in which onlythe minimum and the maximum delivery rate are adjustable, considerablelocking forces are needed to lock the swivel plate in its swivelposition. Said locking forces may admittedly be summoned up by anadjusting element connected to the swivel plate but, for said purpose, avery stable construction of the adjusting element is required. In orderto simplify the design, it has already been proposed, particularly inthe case of swivel plates having a swivel bearing arrangement in theform of a swivel cradle, to provide mechanical stops for limiting theminimum and maximum swivel end position. Given such limitation ofswivelling, the adjusting apparatus is at least relieved of load in theswivel end positions.

[0004] An axial piston engine according to the preamble of claim 5 or 6is described in DE 198 00 631 A1. In said previously known construction,the axial piston engine has a return apparatus, against which thesliding pads are supported during the return motion of the pistons. Theaxial piston engine moreover has a retaining apparatus formed by atleast one supporting part, which axially supports the return apparatusin order to protect it from overload. The supporting part is disposed onthe housing, namely in the region of the swivelling axis of the swivelplate at least at the side of the axial piston engine at which thepistons execute an induction stroke, wherein the supporting part forms astop disposed at a distance from the return apparatus. Because of theaxial distance of the stop and/or supporting part from the returnapparatus it is guaranteed that during normal operation there is nocontact between the supporting part and the return apparatus. It is onlywhen the return apparatus is overloaded and gives axially within itslimit of elasticity that said apparatus comes into supportive contactwith the supporting part and is axially effectively supported, therebypreventing the return apparatus from being overloaded beyond the limitof elasticity and damaged. The arrangement of the supporting part in theregion of the swivelling axis makes it possible for the supporting part,in all swivel positions of the swivel plate, to be situated in relationto the latter in an advantageous contact and support position. Theretaining apparatus is therefore suitable for axial piston engines of avariable or invariable throughput rate.

[0005] The underlying object of the invention is to stabilize an axialpiston engine of the type indicated in the preamble of claim 1 or 5,while guaranteeing a simple construction.

[0006] Said object is achieved by the features of claim 1 or 5.Advantageous developments of the invention are described in theassociated sub-claims.

[0007] In the construction according to the invention according to claim1, the stops are disposed on the sleeve-shaped supporting part, which issupported against the wall of the housing interior.

[0008] In the construction according to the invention according to claim5, the shoulder is disposed on the sleeve-shaped supporting part, whichis supported against the wall of the housing interior.

[0009] Both construction are advantageous for several reasons. First ofall, the stops and/or the shoulder may be realized in a simple style ofconstruction because they are disposed on a single supporting part andmay therefore be manufactured easily, quickly and economically andinstalled by mounting the supporting part. The construction according tothe invention is moreover notable for high built-on stability becausethe supporting part may be supported easily and by a large surface areaagainst the wall of the housing interior. In said respect, thesleeve-shaped form of the supporting part proves advantageous becausethe supporting part may be supported positively against the housing andso easy and stable support is achievable. This applies particularly to asupporting part mounted in an axially displaceable manner, which isdescribed in detail further below.

[0010] A further underlying object of the invention is to construct anaxial piston engine of the type indicated in the preamble of claim 6 insuch a way that the distance situation between the return apparatus andthe supporting part is improved.

[0011] Said object is achieved by the features of claim 6. Advantageousdevelopments of the invention are described in the associatedsub-claims.

[0012] In the construction according to the invention according to claim6, the supporting part is mounted in an axially displaceable manner andloadable by the cylinder drum towards a restoring element in such a waythat with progressive loading by the cylinder drum the distance betweenthe supporting part and the return apparatus becomes smaller. Thus, inthe event of peak loads of the axial piston engine a desirable reductionof the distance between the return apparatus and the retaining apparatusis effected, wherein said reduction is based on the fact that thecylinder drum likewise has a tendency to lift off a cam disk during theinduction stroke of the pistons. Said lifting-off motion is aconsequence of peak loading and/or overloading of the axial pistonengine. The lifting-off motion of the cylinder drum leads, in theconstruction according to the invention, to a reduction of the distancebetween the supporting part and the return apparatus so that, in theevent of peak loading and/or overloading, because of the reduceddistance an effective supporting of the return apparatus is effected.The construction according to the invention therefore provides a meanswhereby, in the event of peak loading and/or overloading of the axialpiston engine, the distance between the supporting part and the returnapparatus is reduced, with the result that the supporting of the returnapparatus comes into effect earlier and is therefore improved.

[0013] The previously described axial distance between the supportingpart and the return apparatus may be e.g. around 1 mm. If the distanceis too small, there is a risk of the return apparatus and the supportingpart coming into mutual contact and of the return apparatus sliding onthe supporting part before overloading of the return device occurs. Ifthe distance is too great, there is a risk of the return apparatus beingoverloaded and damaged, e.g. warped, before the additional supportagainst the supporting part may occur.

[0014] Another aspect of the axial piston engine according to theinvention is such that the supporting part without a shoulder surfacefor the return apparatus and without stops for the swivel plate extendsup to the cylinder drum and is at a sliding distance from the cylinderdrum. In said construction, the supporting part acts as an abutment forthe cylinder drum. Said abutment may replace other axial abutments forthe cylinder drum or be provided as an additional abutment. The functionof an abutment for the cylinder drum is fulfilled also when thesupporting part is mounted in an axially displaceable manner. In such aconstruction, the abutment function is admittedly reduced and limited tothe force of the restoring element, but said restoring force too is anabutment force.

[0015] The supporting part according to the invention may be developedvery advantageously in that it is used both as a stop part for theswivel plate and as a safety retainer for the return apparatus. In saidcase, a simple and stable construction as a sleeve-shaped component isachievable.

[0016] The further sub-claims contain features which, while guaranteeinga stable construction, enable easy and economical manufacture as well asassembly and/or disassembly.

[0017] There now follows a detailed description of the invention andfurther advantages achievable by the invention with reference toadvantageous constructions of embodiments and drawings. The drawingsshow:

[0018]FIG. 1 an axial piston engine according to the invention in axialsection;

[0019]FIG. 2 an enlarged view of the detail denoted by X in FIG. 1;

[0020]FIG. 3 a front view from the left of a supporting part in the formof a sleeve of the axial piston engine;

[0021]FIG. 4 the supporting part in axial section; and

[0022]FIG. 5 the detail X in a modified construction.

[0023] The axial piston engine 1 illustrated by way of example comprisesa closed housing 2 having a pot-shaped housing part 3, the housinginterior 4 of which is detachably closed by means of a so-calledconnecting part 5, which is screw-fastened in the sense of a lid to thefree edge of the housing part 3 by screws 6 shown in an implied manner.Mounted rotatably in the housing 2 is a drive shaft 7, which at leastpartially penetrates the base wall 3 a of the pot-shaped housing 3 in abearing hole 8 and is mounted in a freely rotatable manner by means ofrolling-contact bearings 9, 11 indirectly or directly on the base wall 3a of the pot-shaped housing 3 and on the connecting part 5. Disposedagainst the inside of the connecting part 5 is a cam disk 13 havingcontrol channels 14 a, 14 b, which extend diametrically opposite oneanother approximately parallel to the axis of rotation 7 a of the driveshaft 7 and are connected respectively to a supply line 15 and adischarge line 16 in the connecting part 5. Lying against the inside ofthe cam disk 13 is a cylinder drum 17, which is seated by means of acoaxial longitudinal bore 18 on the drive shaft 7 and connectednon-rotatably thereto by a multitooth coupling 19, which in the presentembodiment is disposed only in an end region of the cylinder drum 17remote from the cam disk 13 and in a longitudinal region of the driveshaft 7 radially adjacent to said end region.

[0024] Disposed in the cylinder drum 17 and distributed around thecircumference is a plurality of approximately paraxially extendingpiston bores 21, which at their ends facing the control channels 14 a,14 b are connected by tapered supply and discharge channels to thecontrol channels 14 a and 14 b respectively and which open out at theend of the cylinder drum 17 remote from the cam disk 13. Pistons 23 aremounted so as to be axially displaceable to and fro in the piston bores21 and with their ends facing the cam disk 13 delimit working chambers24 in the piston bores 21 and with their head ends remote from the camdisk 13 project from the cylinder drum 17 and are axially supported bymeans of supporting joints 25, in particular ball joints, in anobliquely extending transverse plane against a swivel plate 26. Theswivel plate 26, for increasing or reducing the variable throughputrate, is mounted so as to be capable of swivelling about a swivellingaxis 27 extending at right angles to the axis of rotation 7 a and isadjustable by means of an adjusting apparatus 28 preferably disposed inthe housing interior 4 and is lockable in the respective adjustedposition. The swivel plate 26 at its side facing the cylinder drum 17has an inclined surface 26 a, against which the pistons 23 are supportedby means of sliding pads 29, which are connected by the supportingjoints 25 in a universally pivotal manner to the preferably sphericalhead ends of the pistons 23.

[0025] The swivel bearing 30 of the swivel plate 26 thus formed is aso-called cradle bearing or closed bearing, which may be fitted byintroducing the swivel plate 26 from the direction of the housingopening and in the present embodiment is formed by a concave bearingsurface 30 a on the swivel plate 26 facing the base wall 3 a and by amatching convex bearing surface 30 b supported against the base wall 3a, which bearing surfaces extend approximately over an angle of about180°. The swivel plate 26 may therefore be removed from and/or liftedoff the swivel bearing 30 in the direction of the housing opening. Thebase-side bearing surface 30 b may be formed on one or more bearingparts 30 c, which is/are inserted by at least one insertion pin 30 dfacing the base wall 3 a into an insertion hole 3 b in the base wall 3 aand is/are therefore positioned in transverse direction and in thedirection of the base wall 3 a.

[0026] During functional operation of the axial piston engine 1 thedrive shaft 7 and the cylinder drum 17 rotate jointly about the axis ofrotation 7 a, while the pistons 23 are displaced to and fro in thepiston bores 21 by the inclined surface 26 a of the non-rotating swivelplate 26. In said case, the axial piston engine 1 may operate in pumpmode or engine mode. In order to prevent the sliding pads 29 fromlifting off the inclined surface 26 a during the induction stroke, thereis associated with the sliding pads 29 a return apparatus 33, whichkeeps the sliding pads 29 in contact with the inclined surface 26 a andin the present embodiment is formed by a return disk 33, which in aknown manner engages with bore edges 35 behind flanges 29 a of thesliding pads 29. The return disk 34, which preferably extends in astraight manner, is axially supported by a cone-segment-shaped concavebearing surface 37 against a correspondingly cone-segment-shaped convexbearing surface 38 of a supporting ring 39, which is mounted by means ofa bearing bore 41 in an axially displaceable manner on the drive shaft 7and is supported in the direction of the cylinder drum 17. Thesupporting ring 39 is preferably connected by a second multitoothcoupling 19 a in a non-rotatable manner to the drive shaft 7, whereinthe teeth on the drive shaft 7 may be provided jointly for bothmultitooth couplings 19, 19 a and be of a corresponding length.

[0027] To achieve efficient sealing between the cylinder drum 17 and thecam disk 13, the cylinder drum 17 is biased with an axial elastic forcetowards the cam disk 13. In the embodiment according to FIG. 1, pressingforces for the sliding pads 29 and the cylinder drum 17 are generated bya common, axially effective spring 42, which may be disposed e.g.between a supporting ring 43 and the cylinder drum 17 and presses thelatter towards the cam disk 13. The compression spring 42 in the form ofa cylindrical helical spring may act upon the supporting ring 39 bymeans of pressure pins 43 a, which are arranged so as to be distributedaround the periphery of the drive shaft 7 and are mounted in an axiallydisplaceable manner in feedthrough holes of the cylinder drum 17 andextend from the supporting ring 43 to the supporting ring 39.

[0028] For delimiting the minimum and maximum swivel position of theswivel plate 26, one stop 44 or two stops 44 a, 44 b is/are disposed ona housing-fixed supporting part 45, which is common to both stops and issupported and held against the housing wall surrounding the housinginterior 4. In the present embodiment, the supporting part 45 is formedby a ring and/or a sleeve 45 a, which abuts the inner lateral surface 3c of the peripheral wall 3 d of the housing 3 and is axially positioned.For said purpose, a spring ring 46 may be used, which is seated in aninternal annular groove in the inner lateral surface 3 c and engagesbehind a radial end face of the sleeve 45 a. In the direction of theswivel plate 26 the supporting part 45 is supported by means of apositioning apparatus, which is denoted as a whole by 47 and describedin greater detail further below.

[0029] The stops 44 a, 44 b are formed by inclined stop faces 48, 49 onthe end of the supporting part 45 facing the swivel plate 26, theinclination of which stop faces is adapted to the swivel plate 26 insuch a way that the inclined surface 26 a of the latter in the minimumand the maximum swivel end position is in surface contact with therespective inclined stop face 48, 49. In the context of the invention,it is also possible for a different surface of the swivel plate 26 tolie against the stops 44 a, 44 b. Preferably, a surface contact isprovided so that the surface pressure is reduced. The obtuse angle Wincluded by the stop faces 48, 49 is approximately 180° minus anexisting minimum swivel angle and minus the swivel angle of the swivelplate 26 between the swivel end positions.

[0030] In the present embodiment, the adjusting apparatus 28 is formedby a hydraulic cylinder disposed paraxially in the base wall 3 a andhaving a piston 28 a, which is mounted so as to be displaceable to andfro in an approximately paraxial piston bore 28 b and acts with aworking member such as a piston rod 28 c upon the outside of the swivelplate 26. The cylinder is disposed e.g. in relation to the axis ofrotation 7 a at the side of the axial piston engine 1 which is offset inthe opposite direction to the radial offset v of the swivelling axis 27from the axis of rotation 7 a, see offset dimension v2. Because of theoffset arrangement of the swivelling axis 27 and the piston rod 28 c, anadjustment of the swivel plate 26 by means of the cylinder requires onlya translatory motion, which the piston rod 28 c executes after loadingof the adjusting cylinder with an actuating pressure through anactuating pressure line 28 d, which penetrates the add-on joint 3 e in asealed manner and passes with its power connection out of the connectingpart 5. In said case, the swivel plate 26 executes a swivelling motionin the direction of a minimum delivery rate, wherein it is limited atthe stop 44 a in the minimum swivel end position. A restoring of theswivel plate 26 in the direction of its maximum swivel end position iseffected automatically when the hydraulic loading of the piston 28 awith the actuating pressure is discontinued. A resulting axial exhaustpressure of the pistons 23 then arises, by means of which the swivelplate 26 is adjusted in the direction of its maximum swivel end positionand held in abutment against the piston rod 28 c. By means of a spring28 e, in particular a cylindrical helical spring, which is disposedpreferably in a blind hole between the piston 28 a and a remaining partof the base wall 3 a, the abutment of the piston rod 28 c against theswivel plate 26 may be guaranteed also in the non-pressurized state.

[0031] The piston rod 28 c is connected by a supporting joint 25 in anarticulated manner to the piston 28 a. Here too, as already in the caseof the articulated connections between the pistons 23 and the slidingpads 29, a ball joint connection is provided, comprising a sphericalhead, e.g. on the piston rod 28 c, and an undercut ball socket, e.g. onthe piston 28 a.

[0032] In the context of the invention, the hydraulic cylinder mayalternatively be designed in such a way that the restoring of the swivelplate 26 into its maximum swivel end position may be effected activelyby means of the piston 28 a or the piston rod 28 c, which in said casemay be connected to the swivel plate 26 in such a way that they mayexert a tensile force upon the latter.

[0033] If at least one of the two stops 44 a, 44 b on the supportingpart 45 may be disposed on the housing 2, then only one stop, inparticular for the minimum swivel end position, is required on thesupporting part 45. In the present embodiment, a stop delimiting theswivel plate 26 in its maximum swivel end position may be formed in adifferent manner, e.g. by the inner surface of the base wall 3 a,against which the swivel plate abuts. In such a case, it is possible todispense with the relevant stop on the supporting part 45, here the stop44 b.

[0034] As may be seen from FIG. 1, the piston 28 a has a preferablycoaxial channel 28 f, which extends to the spherical bearing surface ofthe ball joint connection and leads in the piston rod 28 c up to thelatter's preferably widened free end face, particularly in the region ofa channel widening. The actuating pressure may therefore continue intothe bed joint of the ball joint and the contact surface of the pistonrod 28 c and generate in each case a relief from pressure.

[0035] In order during functional operation of the axial piston engine 1to prevent overloading of the return apparatus 33 in the event ofincreased tensile forces at the pistons 23, there is associated with thereturn apparatus 33 a retaining apparatus 51, which engages behind thereturn apparatus 33 at a distance a directed towards the cylinder drum17 and supports the return apparatus in the event of extreme loading oroverloading. The distance a is large enough for the return apparatus 33to strike and be axially supported against at least one stop 52 of theretaining apparatus 51 before the return apparatus 33 is loaded beyondits limit of elasticity. It is thereby guaranteed that during normalfunctional operation the small distance a of e.g. 0.4 mm to around 1 mmexists between the return apparatus 33 and the retaining apparatus 51and there is therefore no friction contact between the return apparatus33 and the retaining apparatus 51. In the event of increased pistontensile forces, the return apparatus 33 may follow the loading forces,wherein it is e.g. axially bent. Overloading and permanent deformationof the return apparatus 33 is however avoided because said apparatus,before it is deformed beyond its limit of elasticity, comes intoabutment against the stop 52 of the retaining apparatus 51. This meansthat, in the event of such extreme axial loading of the return apparatus33, the latter is effectively supported and protected from overload bythe retaining apparatus 51 and may therefore after extreme loading, onaccount of its elasticity, return to its normal or initial position, inwhich it is at the distance a from the retaining apparatus 51. Inprinciple, one stop 52 is sufficient, which is disposed at the side ofthe axial piston engine 1 at which the piston tensile forces arise. Insaid case, the stop 52 may be disposed so as to be at the distance afrom the return apparatus 33, in the case of a swivel plate 26adjustable also into intermediate positions, in the respective swivelposition or, in the case of a swivel plate 26 adjustable only into theswivel end positions, in the swivel end positions. The retainingapparatus 51 comprises, in relation to the centre line or axis ofrotation 7 a, preferably one stop 52 on either side, i.e. two stops 52disposed opposite one another, so that the retaining apparatus 51 iseffective also in the event of a functional reversal (pump mode/enginemode).

[0036] In the present embodiment, the retaining apparatus 51 is disposedon the supporting part 45 and formed by one or two mutually oppositeinternal supporting shoulders 53, of which the surfaces facing theswivel plate 26 are shaped and positioned in such a way that, in theswivel end positions, they are at the distance a from the returnapparatus 31, here from the return disk 34. The supporting shoulders 53preferably have flat shoulder surfaces 53 a, 53 b which, viewed in thelongitudinal direction of the swivelling axis 27, extend parallel to andat the distance a from the opposite-lying flat end face of the returndisk 34 in the swivel end positions. When the return apparatus 33 isextremely loaded or overloaded, it may give in the region of thedistance a without damage, wherein it is effectively supported againstthe shoulder surfaces 53 a, 53 b with surface contact and low surfacepressure. In the present construction, the shoulders 53 are formed bymaterial projections, which protrude inwards from the sleeve 45 a andare arranged in a sickle-shaped manner diametrically opposite oneanother, as is shown in FIG. 3. The obtuse angle W1 included by theshoulder surfaces 53 a, 53 b corresponds to the angle W. Since thesickle-shaped material projections extend at right angles to theswivelling axis 27, there are in each case two shoulders 53 lyingopposite one another with shoulder surfaces 53 a, 53 b for the minimumand for the maximum swivel end position.

[0037] When the return apparatus 33 in the event of extreme loading isaxially supported by the retaining apparatus 51, the supporting forceseffective at the retaining apparatus 51, because of the latter beingfastened to and/or supported against the housing 2, are introduced intothe housing 2. In the present construction, the spring ring 46adequately performs said function.

[0038] According to FIG. 5, the supporting part 45 may be a load-bearingbase part of a second retaining apparatus 61, which with at least onesupporting shoulder 62 axially overlaps the cylinder drum 17 at least atthe side, at which the pistons 23 execute an induction stroke, and whichis at a small distance b from the cylinder drum 17, which distanceduring normal operation prevents sliding friction between the cylinderdrum 17 and the supporting shoulder 62. The supporting shoulder 62 maybe disposed directly on the supporting part 45 and/or on the sleeve 45 aor be formed by a supporting ring 63, which is inserted in a tightlyfitting manner between the sleeve 45 a and the spring ring 46, andprojects radially inwards beyond the sleeve wall, wherein it overlaps ane.g. relieved end face portion 17 a of the cylinder drum 17 at thedistance b. Because of the distance b of e.g. likewise approximately 0.4mm to approximately 1 mm, frictionless rotation of the cylinder drum 17next to the supporting shoulder 62 is guaranteed during normalfunctional operation. The cylinder drum 17, if it lifts off the cam disk13 in the event of already described higher piston tensile forces, isretained by the second retaining apparatus 61 so that it may lift off atmost only by the distance b. When the supporting disk 17 abuts againstthe stop 64 formed by the supporting shoulder 62, there is admittedlyfriction between the retaining apparatus 61 and the cylinder drum 17 butsaid functional state exists only provisionally or for a short timeduring extreme loading. The supporting part 45, because of its e.g.rigid positioning 9 on the housing 2, is able to take up the loadtransmitted axially from the cylinder drum 17 to the supporting part 45and transmit it to the housing 2. The supporting shoulder 62 and/or thesupporting ring 63 is preferably coated with a strong material at theside facing the cylinder drum 17.

[0039] In the embodiments illustrated in the drawings, the supportingpart 45 and/or the sleeve 45 a is mounted so as to be axiallydisplaceable and non-rotatable in peripheral direction. To said end, anaxial guide 65 is provided between the peripheral wall 3 d of thehousing 2 and the supporting part 45 and is formed by a paraxial guidejournal 66, which is inserted with motional clearance into a guiderecess 67. The guide journal 66 may be formed by a cylinder 67, which isfitted into a guide groove 67 a of a corresponding cross-sectional shapein the inner lateral surface 3 c of the peripheral wall 3 d and into aguide groove 67 b of a corresponding cross-sectional shape in the outerlateral surface of the sleeve 45 a. Said constructions each also form apositive-action anti-rotational element for the sleeve 45 a in thehousing 2.

[0040] In FIGS. 1, 2 and 5 a single positioning apparatus 47 is shown ina position rotated through 90° in peripheral direction, which isclarified by a partial section of the cutting line S. In reality, oneor, in particular, two positioning devices 47 arranged rotated through90° are provided, which is evident from the existence of two guidegrooves 67 b arranged diametrically opposite one another in the sleeve45 a in FIG. 3.

[0041] To facilitate assembly, the guide grooves 67 a in the peripheralwall 3 d may be extended so as to run out to the add-on surface 3 e ofthe peripheral wall 3 d, which is evident from the partial sections inFIGS. 1, 2 and 5. The guide grooves 67 b in the sleeve 45 a may beextended so as to run out to the inclined end face facing the swivelplate 26, which is likewise evident from the partial sections in FIGS.1, 2 and 5.

[0042] What is essential in the arrangement according to FIG. 5 is thatthe length of the guide journal 66 and the positions of the axiallymutually opposite end faces 67 c, 67 d of the guide grooves 67 a, 67 bare positioned in such a way that in the normal functional position ofthe sleeve 45 a, in which position the latter lies indirectly ordirectly against the spring ring 46, there is a distance c between theend face 67 d, which delimits the guide groove 67 b in the direction ofthe cylinder drum 17, and the end face 66 a of the guide journal 66facing the cylinder drum 17. The distance c is in particular equal to orgreater than the distance b and preferably equal to or greater than thesum of the distances b and a.

[0043] The direct (FIG. 2) or indirect (FIG. 5) abutment of the sleeve45 a against the spring ring 46 is guaranteed by means of an axiallyeffective spring 68, which biases the sleeve 45 a towards the springring 46. The spring 66 may be disposed in the journal 66 designed as asleeve and may be formed preferably by a cylindrical helical spring.Said spring is biased towards the end face 67 d of the guide groove 67 badjacent to the spring ring 46.

[0044] In the embodiment according to FIG. 5, no stops 44 a, 44 b forlimiting the swivelling motion of the swivel plate 26 are provided onthe supporting part 45. This is evident from the fact that the inclinedshoulder surfaces 53 a, 53 b are not axially offset relative to theinclined end face of the supporting part 45, as is the case in theembodiment according to FIGS. 2 to 4. In this embodiment other,non-illustrated stops for limiting the swivelling motions are provided.

[0045] Because of the axial displaceability of the supporting part 45,in the embodiment according to FIG. 5 it is guaranteed that the cylinderdrum 17, as it lifts progressively off the cam disk 13, displaces thesupporting part 45 in the direction of the swivel plate 26 counter tothe action of the spring 66 and reduces or eliminates the distance a ofthe retaining apparatus 51. Thus, in the event of high loads of theaxial piston engine, the return apparatus 33 is axially supported by theretaining apparatus 51 earlier than in the event of lower loads.

[0046] In the axial piston engine 1 the following constructionalvariants are possible and operational.

[0047] When in the embodiment according to FIG. 2 a retaining apparatusfor the return apparatus 33 is provided in a conceivable differentconstruction independent of the supporting part 45, it is possible todispense with the at least one shoulder surface 53 a, 53 b on thesupporting part 45, wherein the supporting part 45 fulfils the stopfunction for the swivel plate 26.

[0048] When, on the other hand, conceivable different stops independentof the supporting part 45 are provided for limiting the swivellingmotion of the swivel plate 26 in its minimum and maximum swivelposition, it is possible to dispense with the stops 44 a, 44 b on thesupporting part 45, wherein only the retaining apparatus 51 need beconstructed on the supporting part 45.

[0049] In both previously described constructional cases, the supportingpart 45 may be a component, which is independent of the conceivablesecond retaining apparatus 61 and is disposed and supported on thehousing 2, as shown in FIG. 2.

[0050] In the context of the invention it is also possible to design thesupporting part 45 merely as a carrier for the second retainingapparatus 61, wherein stops for limiting the swivelling motion and areturn apparatus of different constructions independent of thesupporting part 45 may be provided. In said construction also, thesupporting part 45 may be mounted in an axially non-displaceable manneron the housing 2 or guided in an axially displaceable manner on thehousing 2. The former case results in a fixed axial stop for thecylinder drum 17, when the latter lifts off. The latter case results inan axially elastically flexible stop when the cylinder drum 17 liftsoff.

[0051] When the first retaining apparatus 51 and the second retainingapparatus 61 are disposed jointly on the supporting part 45, uponlifting-off of the cylinder drum 17 the described reduction of thedistance a of the first retaining apparatus 51 arises.

[0052] As may be seen from FIG. 1, a further retaining apparatus 71acting between the cylinder drum 17 and the drive shaft 7 may beprovided, which is effective indirectly between the drive shaft 7 andthe cylinder drum 17 and counteracts a lifting-off of the cylinder drum17. Said further retaining apparatus 71 is formed by an axiallyeffective cup spring 72, which is supported axially against the driveshaft 7 or a built-on part of the latter and overlaps a spring ring 73,which is seated in an internal annular groove of the cylinder drum 17.The dimensions of the associated parts are such that, in the functionalposition of the cylinder drum 17 in abutment against the cam disk 13,the cup spring 72 indirectly via the spring ring 73 biases the cylinderdrum 17 towards the cam disk 13 or limits the cylinder drum. The cupspring 72 may moreover be bent elastically in the direction of theswivel plate 26. Said restoring force is set high enough to allow thecylinder drum 17, in the event of high piston suction forces or relatedoverloads, to lift off axially from the cam disk 13. If the lifting-offmotion exceeds the dimension b, the supporting part 45 is displaced inthe direction of the inclined surface 26 a, and the prescribed distancea is reduced. The axial force of the at least one spring 68 ispreferably set lower than the axial force of the cup spring 72.

1. Axial piston engine (1) having a housing (2), in the housing interior(4) of which a cylinder drum (17) is mounted, in which a plurality ofapproximately axially extending piston bores (21) are formed, which arearranged so as to be distributed around the longitudinal centre line (7a) of the cylinder drum (17) and in which pistons (23) are movablyguided, which are supported via sliding pads (29) against a swivel plate(26) mounted so as to be capable of swivelling about a transverselyextending swivelling axis (27), wherein one stop (44 b) or one stop (44a, 44 b) disposed on either side of the swivelling axis (27) is or areprovided for limiting the swivelling motions of the swivel plate (26),characterized in that the stop (44 b) or both stops (44 a, 44 b) aredisposed on a sleeve-shaped supporting part (45), which is supportedagainst the inner lateral surface (3 c) of the housing interior (4). 2.Axial piston engine according to claim 1, characterized in that the stopor stops (44 a, 44 b) are formed by stop faces (48, 49), with which theswivel plate (26) is in surface contact, preferably by means of aninclined surface (26 a), against which the sliding pads (29) aresupported.
 3. Axial piston engine according to claim 1 or 2,characterized in that the stop face or stop faces (48, 49) are disposedon the end face of the supporting part (45) facing the swivel plate(26).
 4. Axial piston engine according to one of the preceding claims,characterized in that a return apparatus (33) is provided, against whichthe sliding pads (29) are supported during the return motion of thepistons (23), and on the supporting part (45) a retaining apparatus (51)is disposed, which engages at an axial distance (a) behind the returnapparatus (33) at the side remote from the swivel plate (26).
 5. Axialpiston engine (1) having a housing (2), in the housing interior (4) ofwhich a cylinder drum (17) is mounted, in which a plurality ofapproximately axially extending piston bores (21) are formed, which arearranged so as to be distributed around the longitudinal centre line (7a) of the cylinder drum (17) and in which pistons (23) are movablyguided, which are supported via sliding pads (29) against an inclinedsurface (26 a) of a swivel plate (26), and having disposed on thehousing (2) a first retaining apparatus (51) with a supporting part (45)with a shoulder (53) for supporting a return apparatus (33) against thehousing (2), wherein the shoulder (53) is disposed at the side of theaxial piston engine (1) at which the pistons (23) execute an inductionstroke, and wherein the shoulder (53) engages at an axial distance (a)behind the return apparatus (33) at the side facing the cylinder drum(17), characterized in that the shoulder (53) is disposed on asleeve-shaped supporting part (45), which is supported against the innerlateral surface (3 c) of the housing interior (4).
 6. Axial pistonengine (1) having a housing (2), in the housing interior (4) of which acylinder drum (17) is mounted, in which a plurality of approximatelyaxially extending piston bores (21) are formed, which are arranged so asto be distributed around the longitudinal centre line (7 a) of thecylinder drum (17) and in which pistons (23) are movably guided, whichare supported via sliding pads (29) against an inclined surface (26 a)of a swivel plate (26), and having disposed on the housing (2) a firstretaining apparatus (51) with a supporting part (45) with a shouldersurface (53 a, 53 b) for supporting a return apparatus (33) against thehousing (2), wherein the shoulder surface (53 a, 53 b) is disposed atthe side of the axial piston engine (1) at which the pistons (23)execute an induction stroke, and wherein the shoulder surface (53 a, 53b) engages at an axial distance (a) behind the return apparatus (33) atthe side facing the cylinder drum.(17), characterized in that thesupporting part (45) is mounted in an axially displaceable manner and isloadable by the cylinder drum (17) towards a restoring element in such away that with progressive loading by the cylinder drum (17) the distance(a) becomes smaller.
 7. Axial piston engine according to claim 6,characterized in that the supporting part (45) is a sleeve-shapedcomponent, which is mounted in an axially displaceable manner on theinner wall of the housing (2).
 8. Axial piston engine according to claim6 or 7, characterized in that the supporting part (45) overlaps thecylinder drum (17) at an axial distance (b) at the side facing theswivel plate (26).
 9. Axial piston engine according to one of claims 5to 8, characterized in that the retaining apparatus (51) comprises twoshoulders (53), which are disposed in relation to the swivelling axis(27) on either side of the axial piston engine (1) and are directedtowards the swivel plate (26) and, given the provision of one or twostop faces (48, 49), are offset relative to the latter axially in thedirection of the cylinder drum (17) and radially inwards.
 10. Axialpiston engine according to one of claims 5 to 9, characterized in thatthe shoulder (53) or the shoulders (53) is or are formed in each case bya shoulder surface (53 a, 53 b).
 11. Axial piston engine according toclaim 10, characterized in that mutually associated stop faces andshoulder surfaces (48, 49, 53 a, 53 b) extend in each case parallel toone another.
 12. Axial piston engine according to one of claims 5 to 11,characterized in that the shoulder (53) or the shoulders (53) or theshoulder surface (53 a, 53 b) or the shoulder surfaces (53 a, 53 b) isor are disposed in each case on a material projection protrudingradially inwards from the sleeve-shaped supporting part (45).
 13. Axialpiston engine according to one of the preceding claims, characterized inthat the supporting part (45) is supported by an end face remote fromthe swivel plate (26) against a supporting shoulder (46) on the housing(2) and is held by rigidly or flexibly acting means against thesupporting shoulder (46), which is preferably formed by a spring ring(46).